Studies of stoichiometry, energetics and kinetics of electron transfer reactions are being conducted for the purpose of understanding the mechanism of biological electron transfer components. Efforts are presently concentrated on the components such as the heme proteins (cytochrome c and cytochrome c oxidase) in the mammalian respiratory system. An important part of this proposal is the development and application of the indirect coulometric titration and spectroelectrochemical methods using optically transparent electrodes.